The present invention relates to a water-resisting structure for a watch such as a diver's watch.
When a diver works under water for a long period, the diver stays in a capsule and gets out the capsule when working. The air in the capsule is kept at a high pressure according to the depth of the position where the capsule is anchored. If the diver stays in the capsule for a long period, nitrogen in the air in the capsule gradually permeates the blood of the diver.
The nitrogen in the blood anesthetizes the diver and when the amount of nitrogen exceeds a saturation condition, the nitrogen vaporizes, which endangers the like of the diver.
In order to avoid such dangers, the capsule is filled with air in which nitrogen is substituted with harmless helium gas. However, the helium gas has a permeability through the packings used in a diver's watch. Therefore, the helium gas in the capsule gradually enters into the watchcase of the diver's watch through the packings.
As a result, the inner pressure in the watchcase increases as high as that of the capsule. When the capsule is raised, the pressure in the capsule is gradually reduced to return to atmospheric pressure in order to avoid submarine sickness. However the helium gas in the watchcase does not quickly leak out, so that the inner pressure of the watchcase becomes higher than the atmospheric pressure. A large difference between both pressures results in breaking of the glass of the diver's watch or the falling off of parts of the watch.
FIG. 1 shows a conventional watchcase of a diver's watch provided with a structure for exhausting helium gas. A case body 1 has a radial bore 2 having a shoulder 2a formed on an inner end portion thereof and a thread 2b formed on an outer end portion thereof. In the hole 2, an O-ring 3 is engaged with the shoulder 2a and a compression member 4 is engaged with the O-ring 3. A spring 5 is provided between the compression member 4 and another compression member 6 threaded into a thread 2b for urging the compression member 4 to the O-ring 3. The compression member 6 has a perforation 7 for communicating the interior with the atmosphere. A gap is provided between the compression member 4 and the inner wall of the hole 2.
For a long stay in a capsule, helium gas gradually enters into the watchcase through the O-ring 3 so that the inner pressure of the case becomes rather high. During the reduction of the inner pressure of the capsule, since the inner pressure of the watchcase becomes higher than that of the capsule, the compression member 4 depresses the spring 5 against its elasticity. Thus, the compression force to the O-ring 3 is decreased to leak the helium gas in the watchcase through gaps.
However, in such a structure, the thickness of the watchcase is increased because of many structural parts and the bore 2 is exposed to the outside, which impairs the appearance of the watch.